PicoSAT

With release 965 we support inclusion of PicoSAT into R projects
thanks to Christoph M¨ssel (see BoolNet),
which also led to more clean code related to the usage of pointer
differences. The all-difference-constraint code was partially
revived (thanks to Himanshu Jain). We also added support for our
new generic incremental SAT solver interface ipasir.h
as used in the incremental track of the last SAT Race'15.

Version 960 fixes severals issues found by Stefan Hengelein. and
version 957 contains several fixes for bugs in
'picosat_deref_partial' reported by Rüdiger Ehlers.

Version 953 became reentrant. This allows multiple PicoSAT
instances in the same process. This changes most of API functions
which now require an additional PicoSAT manager object as first
argument. In version 954 we define the macro
PICOSAT_REENTRANT_API in the header file. The previous
release 951 is a cleaned-up version after incorporating comments by
Donald Knuth.

PicoSAT uses an MIT style license. In essence, you can use and
modify the sources as you like provided that you acknowledge the
origin of the software in the source code. More details can be
found in the LICENSE file that comes
with the sources.